async findUserById(userId: number, loggedUserId: number): Promise<UserDTO> {
    const foundUser: User = await this.usersRepository
      .findOne({ where: { id: userId, isDeleted: false }, relations: ['followers'] });

    if (!foundUser) {
      throw new NotFoundUserError();
    }

    const isFollowed: boolean = loggedUserId !== -1 &&
      foundUser['followers'].some((u: User) => u.id === loggedUserId);

    return {
      ...this.mapper.toUserDTO({ ...foundUser }),
      isFollowed,
    };
  }